Conduit selection for right ventricle outflow tract (“RVOT”) reconstruction presents a challenge in the treatment of many congenital heart diseases including tetralogy of Fallot with pulmonary atresia, truncus arteriosus, transposition of great arteries with pulmonary stenosis, congenital aortic stenosis/insufficiency, and variants of such conditions. After the invention of the cryopreservation process in early 1980s, and especially with the increased availability of a wide range in graft sizes, homografts have become the conduit of choice for physicians performing RVOT reconstruction procedures. Such homografts, in many instance, may be used to replace Dacron conduit-mounted stented glutaraldehyde-treated porcine aortic valve heterografts. However, longitudinal studies have demonstrated that homografts may also require conduit replacement due to stenosis, shrinkage, calcification, and insufficiency, especially for younger patients.
Recently, xenograft designs have been evaluated for RVOT reconstruction. Non-limiting examples of such xenografts may include glutaraldehyde-fixed porcine aortic valves and roots, and glutaraldehyde-fixed segments of bovine jugular veins including venous valves. Although the anatomical shape of porcine aortic valves may prove useful in RVOT procedures, stenosis and calcification issues may still persist when such xenografts are implanted in children. Similarly, early fibrotic rind formation at the distal anastomosis, as well as significant conduit dilation and regurgitation may occur following the use of the bovine jugular veins. Thus, allografts and xenografts may prove to be insufficient replacements in RVOT procedures due to their poor hemodynamic performance and recurrent stenosis/insufficiency, especially in very young patients. As a result, multiple RVOT surgeries may be required until the pediatric patient reaches adulthood.
Implanted artificial (that is, non-biological) valves may require fewer replacement surgeries than valves having a biological origin. However, such artificial valves may require significant anticoagulant therapy, especially for valves placed in the pulmonary blood stream. Additionally, replacement artificial valves for use in pediatric/neonatal populations may be limited due to the need to custom design the valves based on intensive bioengineering studies. It may be appreciated, therefore, that there is a need for valved conduits with extended durability, especially for younger patients.
An expanded polytetrafluoroethylene (hereafter, ePTFE) valved conduit for pediatric RVOT reconstruction may include a valve design based on the surgical experience of a physician, or the results from a computer-optimization routine specific for non-expansible conduits.
Such non-expansible conduits can provide good functionality and resistance to thrombosis, stenosis, and calcification. However, the non-expansible conduit may not be capable of accommodating the changes in anatomical structures during patient growth. Somatic growth in pediatric patients can result in the need for replacement of implanted heart valves due to stenosis and other complications if the conduit or a valved conduit is not able to accommodate the anatomic or physiological changes due to patient growth.
At present, there appears to be no conduits for the reconstruction of a pediatric patient's right ventricular outflow tract (RVOT) having long-term patency, a functional valve, and no thrombogenicity. Anti-thrombogenic materials and optimal valve designs can produce good initial results. However, young children may quickly outgrow the implanted conduits and may require reoperation and replacement. To date, only tissue-engineered conduits or valved conduits have been proposed to accommodate patient growth, but these solutions are time- and cost-intensive and still generally unproved for long-term functionality.